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''Halobates'' or sea skaters are a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...
with over 40 species of
water striders The Gerridae are a family of insects in the order Hemiptera, commonly known as water striders, water skeeters, water scooters, water bugs, pond skaters, water skippers, or water skimmers. Consistent with the classification of the Gerridae as tr ...
. Most ''Halobates'' species are coastal and typically found in sheltered marine habitats (a habitat where a few other
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencl ...
of water striders also live), but five live on the surface of the open ocean and only occur near the coast when storms blow them ashore. These are the only known truly oceanic, offshore insects.Marine Insects
. ''Halobates Life.'' Retrieved on 9-09-2009.
They are found in tropical and
subtropical The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...
marine habitats around the world, with a single species recorded in rivers a few kilometers upstream from the ocean. ''Halobates'' are generally very common. They were first collected by
Johann Friedrich von Eschscholtz Johann Friedrich Gustav von Eschscholtz (1 November 1793 – 7 May 1831)Sterling (1997) was a Baltic German physician, naturalist, and entomologist. He was one of the earliest scientific explorers of the Pacific region, making significant collec ...
, a doctor who was part of a Russian expedition aboard the ''Rurik'' between 1815 and 1818. A fossil species ''H. ruffoi'' is known from 45 million year old deposits in Verona, Italy. Close relatives of the genus include '' Austrobates'' and ''
Asclepios Asclepius (; grc-gre, Ἀσκληπιός ''Asklēpiós'' ; la, Aesculapius) is a hero and god of medicine in ancient Greek religion and mythology. He is the son of Apollo and Coronis, or Arsinoe, or of Apollo alone. Asclepius repres ...
''.


Appearance

They are small insects with a body that is up to long and broad, and a leg span up to at least . They lack wings, have long antennae, short front legs used for catching prey (and, in the male, for holding the female during breeding), long middle legs used for propulsion, and somewhat shorter rear legs used for steering. The nymphs resemble miniature versions of the adult. The sexes are quite similar, except that males are thinner than females and have the rear part of the body modified into genitalia, and when gravid the females may have a notably plump abdomen. The various species closely resemble each other in general appearance.


Range and abundance

''Halobates'' are found in tropical and
subtropical The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...
marine habitats around the world. They generally prefer temperatures of , are infrequent below and only exceptionally recorded in waters less than . The coastal species are largely restricted to the
Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
region, with the exception of ''H. robustus'' from the
Galápagos Islands The Galápagos Islands ( Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...
. Some of these coastal species have very small ranges, often restricted to a single archipelago, while others are more widespread. They primarily occur near
mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in sever ...
or other marine plants. A single species, ''H. acherontis'', has been recorded in rivers a few kilometers upstream from the ocean. The absence of coastal species in the Atlantic region may in part be explained by '' Trochopus''. That genus of veliid water striders inhabit coastal mangrove areas in the Atlantic region; the same
niche Niche may refer to: Science * Developmental niche, a concept for understanding the cultural context of child development *Ecological niche, a term describing the relational position of an organism's species * Niche differentiation, in ecology, th ...
inhabited by coastal ''Halobates'' in the Indian and Pacific oceans. The five offshore, pelagic species are ''H. micans'', ''H. germanus'', ''H. sericeus'', ''H. splendens'' and ''H. sobrinus'', of which the last four are found in the Indian and/or Pacific Oceans. ''H. micans'' has a circumglobal range, occurring offshore in warmer seas around the world from about 40° north to 40° south, and it is the only one found in the Atlantic Ocean, including the Caribbean. Their occurrences are generally patchy, but where found they can be very common. During scientific surveys with relatively fast-moving surface nets, they are caught in more than 60% of the tows (less in slow-moving tows, likely because of their ability to avoid them). Studies show that densities locally can be as high as 1 individual per in the oceanic species, and 120 individuals per m² (11 per sq ft) in breeding aggregations of the coastal species.


Behavior and predators

They are
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...
s, with coastal species feeding mainly on land-living insects that have fallen into the water. Less is known about the feeding of the oceanic species, but they appear to mostly eat
zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
, with other recorded items being floating insects, fish eggs and
larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...
, and dead jellyfish. Small prey is caught and eaten by a single ''Halobates'', but larger prey such as small fish may be eaten by three or four ''Halobates'' at once. Adults may
cannibalize Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, bo ...
their own
nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
, and old nymphs cannibalize young nymphs, but generally they do not eat their own age class. Some species prefer struggling prey over immobile prey, but in other species, it is the other way around. The feeding behavior of the newly-hatched nymphs is unknown, as aquarium kept individuals refused to eat the various organisms that older captive nymphs and adults will eat (for example, dead
fruit flies Fruit fly may refer to: Organisms * Drosophilidae, a family of small flies, including: ** ''Drosophila'', the genus of small fruit flies and vinegar flies ** ''Drosophila melanogaster'' or common fruit fly ** '' Drosophila suzukii'' or Asian fruit ...
). This has resulted in speculations that the newly-hatched nymphs might feed on organic-rich surface film. ''Halobates'' may catch aquatic prey just below the surface with their front legs, but do not dive. They are very fast and can reach speeds of per second. The coastal species lay their eggs close to the water surface on rocks, plants, and other structures near the shore, while the oceanic species attach their egg masses on floating objects such as
cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopod A cephalopod is any member of the moll ...
and feathers. Each female lays 1–20 whitish or translucent eggs that each measure about long and half that wide. They may hatch just above or just below the surface. In recent decades the oceanic species have been documented laying their eggs on floating
plastic waste Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are categ ...
, which potentially may disrupt the marine food chain, as the ''Halobates'' (now with access to more surfaces for breeding) may become far more common than usual.Big rise in North Pacific plastic waste
''BBC''
In one extreme case, a plastic gallon jug was found to be covered by 15 layers of eggs, equalling about 70,000 in total. Some species of
storm petrel Storm-petrel may refer to one of two bird families, both in the order Procellariiformes, once treated as the same family. The two families are: *Northern storm petrels (''Hydrobatidae'') are found in the Northern Hemisphere, although some species ...
actively feed on ''Halobates'', sometimes splashing the water with their feet to attract or detect sea striders. Other
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...
s (especially noddies) and a range of surface-feeding fish will also eat them.


Open research questions

Apart from understanding how exactly ''Halobates sp.'' came to be the only genus of insects to live on the open ocean – in spite of insects making up the majority of all animals – those animals offer unique research questions that could have applications in materials sciences. For example, it is still unknown how they can move on the water surface without slipping, but yet their legs are capable of effortlessly detaching from the surface in order to jump. Incapable of diving or hiding, ''Halobates'' must protect themselves from ultraviolet radiation. Although it is known that the
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
of ''Halobates sericeus'' filters more than 99.9998 percent of the UV radiation at the 280 nm wavelength, the chemical properties that confer this protection are still unknown.


References


External links


Halobates
{{Taxonbar, from=Q1686707 Gerromorpha genera Halobatinae Aquatic insects Fauna of the Pacific Ocean Marine insects